A measurement of radio signal strength, e.g. a Received Signal Strength Indicator (“RSSI”), can be used to estimate a distance of a device that is emitting the radio signal, e.g. a mobile device. Fixed radio receivers can also be used to triangulate a location of a mobile device. Mobile device locations can also be determined using Global Positioning System (GPS) signals.
Like reference numbers and designations in the various drawings indicate like elements.